Vibrational frequency shifts measured in all supercritical fluid systems at ρ r = 0.7. Left column: solute, measured band, and solvent. Cited references and measured temperatures are listed in Table I. Str: stretching mode, def: deforming mode, c-: cis-, t-: trans-, pNA: p-nitroaniline, MeOH: methanol, EtOH: ethanol, and p-ABN: p-aminobenzonitrile.
Thermodynamic states for Raman spectral measurements on (a)–(f) pressure-temperature and (g)–(l) density-pressure phase diagrams. Solid lines in Figs. (a)-(f) are the liquid-vapor coexistence curves. Solid lines in Figs. (g)–(l) are visual guides obtained by fitting polynomial functions to the data. The term ρ r is the reduced density represented by ρ r = ρ/ρ c.
(a) Typical example of Raman spectra of trans-stilbene in supercritical fluid. The band at around 1640 cm−1 has been assigned to the C=C stretching mode (see Ref. 5). (b, c) Density dependences of C=C stretching modes of trans-stilbene in (b) scCHF3 and (c) scCO2. Solid lines are the curve fits using the Lorentzian functions. The term ρ r is the reduced density represented by ρ r = ρ/ρ c. In the manuscript, we obtained the peak frequencies of C=C stretching modes by analyzing the spectra using Lorentzian functions.
Frequency shifts of C=C stretching modes of trans-stilbene (red), cis-stilbene (Ref. 10) (pink), and cis-C2H2Cl2 (Ref. 11) (black) in scCHF3 at T r = 1.02. Solid lines are visual guides obtained by fitting polynomial functions to the data.
(a, b) Repulsive (green), net (black), and attractive (red) shifts of C=C stretching modes of trans-stilbene in (a) scCHF3 and (b) scCO2 at T r = 1.02. (c, d) Attractive shift of trans-stilbene (closed circle), cis-stilbene (open circle), and cis-C2H2Cl2 (+) in (c) scCHF3 and (d) scCO2. Solid lines are visual guides obtained by fitting the polynomial functions to the data.
(a) The method to obtain the local density augmentation, (ρ local − ρ)/ρ c. Symbols are experimental attractive shifts. Solid line is linear line based on the mean field approximation. (b, c) Local density augmentations of (b) cis-stilbene and (c) trans-stilbene in scCO2. The quantity of ρ r is expressed as ρ r = ρ/ρ c. Solid lines are visual guides obtained by fitting polynomial functions to the data.
Attractive shifts of C=C stretching modes of (a) trans-stilbene and (b) cis-stilbene (Ref. 10) in scCHF3 (blue) and scCO2 (red) at T r = 1.02.
Systems, temperatures, and references of the data in Fig. 1. The number in the left column represents the order of the shifted amount at ρ r = ρ/ρ c = 0.7, as shown in Fig. 1.
Molecular parameters for calculations of the repulsive shifts.
Dispersion (dis), dipole-induced-dipole (DID), and dipole-dipole terms in Ref. 44.
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